Why is ?

This formula will be useful for some questions in O Level Additional Maths, or A Level H2 Maths.

There are two ways to show or prove this, first we can let

Taking natural logarithm (ln) on both sides, we get

So . Substitute the very first equation and we get . 🙂

Alternatively, we can view and as inverse functions of each other. So, we can let and . Then, by definition of inverse functions. This may be a better way to remember the result. 🙂

The above method of inverse functions can be used to remember too.

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